Latent bulkable yarns have previously been disclosed in the art. Such yarns have generally fallen into one of two classifications, i.e., (1) different polymer materials or (2) different drawing and relaxing conditions, such that when two yarns are combined, they have different shrinkage or elongation properties. Numerous variations in the above basic processes are known to provide different combinations of process steps and/or resulting properties.
The primary deficiency with the previous processes have been that the polymers had to be different, thus requiring separate spinning processes or complex heterofilament spinning systems or the yarns had to be separately drawn and/or relaxed prior to combining so as to achieve the desired differentiation of shrinkage and/or elongation properties. The present process uses the same polymer in a single spinning operation without a separate drawing step. Not only is the same polymer used, it is spun from the same spinneret, thus additionally eliminating separately spinning a second polymer and combining differently spun fibers into a singles yarn.
It is therefore an object of the present invention to produce a latent heat bulkable yarn from the same polymer spun from the same spinneret and spinning column.
It is another object of the present invention to provide a latent heat-bulkable yarn without the requirement of a drawing step.
It is yet another object of the present invention to produce a latent heat bulkable yarn in which the individual fibers have a difference in shrinkage of up to 60 percent, thereby enabling the production of substantial bulk in the resulting yarn.
These and other objects will become apparent from the description of the process and product which follows.